Rotary fluid displacement pump



May 19, 1959 A. w. SAY 9 2,887,064

ROTARY FLUID DISPLACEMENT PUMP Filed Aug. 10, 1954 2 Sheets-Sheet 1 May19, 1 5 I A. w. SAY 2,887,064

United St ms Patent 0,

ROTARY FLUID DISPLACEMENT PUMP Alan William Say, Upminster, England,assignor to The Plessey Company Limited, Ilford, England, a company ofGreat Britain Application August 10, .1954, Serial No. 448,978

Claims priority, application Great Britain September 21, 1953 4 Claims.(Cl. 103-426) This invention relates to rotary fluid displacement pumps,particularly but not exclusively, to pumps rotating at high speeds forhandling volatile liquids at high pressure.

In high pressure gear pumps it is known that corrosion or destructionsimilar to corrosion in appearance is liable to be encountered at theside faces of the casing or of side members eiiecting the seal with theside faces of the gears, in the vicinity of the zone of intermesh. Witha view to reducing this destruction, it has been a wide-spread practiceto recess the side faces of the casing or the like by forming a grooveextending from a point in the zone of intermesh near the planecontaining the axes of the two intermeshing gears to a point freelycommunicating with the pump delivery. While this known expedientnecessarily removes the sealing eifect of the gear intermesh up toapproximately the middle of the zone of intermesh, the present inventionhas for an object to provide improved means for combating the tendencyto gradual destruction of the side walls or the like facing the gearswithout the need of reducing in this manner the effectiveness of theseal due to, the intermesh of the gears. Another object is to provideimproved destruction-reducing means which are suitable for theincorporation in a pump having pressure loaded end plates or bushes.

I have discovered with rotary displacement pumps generally there is atendency for the separation of air and/ or vapour from the liquid atpoints of relatively low pressure in the vicinity of the inlet side ofthe pump. This vapour or air passes through the pump and is separatedfrom the liquid by centrifugal effects so that it accumulates in thespaces at the root of the rotors. When these spaces reach the highpressure zone, there is a sudden application of pressure to the liquidcausing the bubbles to collapse and the liquid impinge against the sidefaces of the casing or bushings with the result that these faces becomepitted or erosion occurs to such an extent that the damage aifects theperformance of the pump. In the case of high speed pumps having bushingsof relatively soft material the damage is very prominent and the life ofthe pump is considerably reduced.

An object of this invention is to overcome this defect and therebyimprove the overall efliciency and life of the pump.

According to this invention means are provided for enabling the airand/or vapour trapped in the spaces at the root of the rotors to bedispersed to an intermediate position transversely between the sides ofthe rotors as each space approaches the pressure zone, whereby the airand vapour accumulated is removed from attacking the side faces of thecasing or bushings when the said spaces reach the pressure zone.

The means for eliminating the erosion may consist of a channel or thelike which communicates with the high pressure zone in such a mannerthat the spaces at the root end of the rotors are brought intocommunication 2 with the high pressure zone before they reach the highpressure side.

The invention will now be described with reference to the accompanyingdrawing in which- Fig. 1 is a side view in section and partly inelevation of a gear pump incorporating the improvement.

Fig. 2 is a section on B-B of Fig. 1 and Fig. 3 is a section on C-C ofFig. 1.

Referring to the drawing- The gear pump comprises a pump housing 1having a removable cover plate 2 at one end, the cover plate beingsecured in position by a ring of screws 3 which are screwed into tappedholes in the end of the pump housing 1.

The pump housing 1 is bored to provide parallel cylindrical intersectingbores 5, 6, with an inlet port 7 and an outlet port 8 at the juncture ofthe bores 5, 6.

Gear wheels 9, 10 with oppositely extending journals 11, 12, 13, 14- areprovided with four bearing bushes 15, 16, 17, 18, interposed between thehousing 1 and gear wheels 9, 19, so that when assembled into the housing1 two opposite pump chambers are formed in the overlapping cylindricalbores. Each of the bearing bushes 15, 16, 17, 13 is formed with anoutwardly extending flange denoted generally by the numeral 19, and theabutting surfaces of the flanges 19 are flat as indicated at 4 in Fig.3. Fluid from the delivery side of the pump is supplied to chanmber 21and a rubber sealing ring 20 is provided for each bushing which servesto prevent leakage of pressure fluid from the chamber 21.

In accordance with the invention a groove 22 is cut in the face of theflanges 19 in the vicinity of the outlet port or pressure zone 8, saidgrooves 22 are so disposed that they extend beyond the pressure zone 8to a point at the root of each of the gears 9, 10, at which theperiphery of the tooth gaps is still sealed by the walls of the bores 5and 6. As a result of this during rotation the spaces at the root of theteeth of said gears 9, 10 successively communicate with the groovesleading to the pressure zone before the spaces reach or connect with thedelivery port 8. By this means any vapour accumulated in the root of thetooth space is flushed away from the vicinity of the side faces of theflanges 19, thereby obviating the disadvantages and defects ashereinbefore set forth.

The invention has been described with reference to the drawing asapplied to a pressure loaded type of pump, but it is to be understoodthe invention is in no way limited to this type of pump. It isapplicable generally to gear types of pumps.

I claim:

1. In a gear pump comprising a pair of intermeshing gear wheels mountedfor rotation in a pumping chamber defined by peripheral walls in sealingcontact with the circumference of the gear Wheels except for an inletchamber and a delivery chamber respectively formed at the two sides ofthe zone of intermesh. and side wall members in sealing contactrespectively with the side faces of the gear teeth at the two sides ofthe gear wheels, the provision, in the surface of each side member, of agroove extending from a first point facing said delivery chamber to asecond point facing the root zone only of one of said gear Wheels in thevicinity of the radial plane defining the limit of sealing contactbetween the gear teeth of said gear wheel and the peripheral Wall of thegear housing, said second point being so selected that when the rootzone of a tooth gap reaches said second point, such tooth gap iscompletely sealed from the delivery chamber by the contact of the gearteeth defining said gap with the peripheral wall and the side wallmembers, said groove being substantially clear of the zone assaoea inwhich the tooth gaps of the gear wheel are sealed by intermeshingcontact of the gear teeth of said gear with those of the other gear.

2. In a gear-type positive-displacement pump having a pair ofintermeshing gear rotors rotatable in a pumping chamber having aperipheral wall in sealing co-operation with the circumference of thegear rotors except for an inlet chamber at one side and an outletchamber at the other side of the zone of inter-mesh, and has side wallsin contact respectively with the two side faces of each gear, thefeature that each side wall is provided with a groove extending from thedelivery chamber to a point which faces the root zone only of each gearrotor adjacent the outlet port in a sector in which the outer parts ofthe teeth of said gear are still in sealing co-operation with theperipheral and side walls, the cross section of said groove beingsufiicient for producing a flushing effect scavenging air or vapourbubbles away from the end of the tooth gap.

3. A gear pump including a housing having a pair of parallel overlappingcylindrical bores, gear rotors in said bores having teeth meshing in thearea of said overlapping bores, said gears having pairs of oppositelyextending journals, bearing bushes associated with said gear rotors andhaving side faces engaging adjacent gear side faces, said housing beingprovided with an inlet port and an outlet port, wherein a groove isformed in the side faces of the bearing bushes, said groove extendingfrom the outlet port to a point passed by the roots only of the toothgaps of each gear wheel while the outer part of such tooth gaps is.still sealed from the outlet port, said groove being substantiallyclear of the zone of sealing intermesh between the teeth of the gearwheel.

4. A gear type positive displacement pump including a housing having apair of parallel overlapping cylindrical bores, gear rotors in saidbores having teeth mesh ing in the area of said overlapping bores, saidgear rotors having a pair of oppositely extending journals, bearingbushes associated with said gear rotors and having side faces engagingadjacent gear side faces, said housing being provided with an inlet portand an outlet port, wherein grooves are formed in the side faces of thebearing bushes, said grooves extending from the outlet port to pointsfacing the roots only of the tooth gaps of each gear rotor while theouter part of such tooth gaps is still sealed from the outlet port, saidgrooves being arranged parallel to the plane containing the axes of thetwo rotors and at such a distance from said plane as to be substantiallyclear of the zone in which the tooth gaps of such rotors are mutuallysealed by intermeshing.

References Cited in the file of this patent UNITED STATES PATENTSNewmier Feb. 13, 19 57

